Dirty air ducts causing problems

When I first got into our home, there was already a central air furnace and central cooling system in the house.  The Heating plus A/C proposal was fairly aged, but still seemed to operate pretty well.  Although I got a licensed supplier to inspect and serviced both the furnace and the cooling system, I never meant to look at the duct system.  It never came to myself and others to have the duct device checked out or cleaned.  The main problem of the air duct is concealed in the walls, ceilings and crawl areas.  Since it’s way out of sight and nearly not easy to access, I didn’t give it a thought.  Despite owning the cooling system and furnace professionally cleaned and took care of every seasonal change, I noticed a small decrease in performance.  The Heating plus A/C proposal gradually began to run longer and longer to achieve a comfortable amount.  It struggled to meet the needs on easily hot or harshly freezing days.  My weekly energy bills became more and more expensive.  I also had seen more dust floating around in the air than usual.  Also, the heated and cooled air from the air registers did not smell all that great.  I at last called our official Heating plus A/C supplier and explained the situation.  She instantly told me about air duct cleaning.  I was a little upset that she had never recommended this at all earlier.  She brought in a huge piece of metal that looked a lot prefer our vacuum cleaner.

air vents